1. Field of the Invention
This invention relates generally to an improved self-propelled grass mowing machine of the tri-plex type having a plurality of cutting units (e.g., three cutting units). Such a machine includes a powered body or traction unit which carries an operator who drives and controls the machine. More particularly, this invention relates to the brake system for the drive wheels of such a mowing machine including the structure and function of the brake shaft assembly.
2.Description of the Prior Art
Grass is a widely used ground for both private and public property. However, grass covered areas are sometimes very large which presents difficult problems in keeping the grass properly mowed. It is not uncommon for cemeteries, golf courses, parks, highway median strips, and the like to extend over many acres of land and be wholly or partially covered by grass. Such large areas usually are not capable of being efficiently mowed by "small scale" or household grass cutting equipment, such as a hand pushed walk-behind lawn mower. Furthermore, at least some of these large grass covered areas must be frequently mowed. For example, the grass on a golf course or cemetery must be mowed as often as once a week or more, especially during the height of the grass growing season. This further dictates against the use of small scale lawn mowing equipment. If such equipment were used to cut such large areas, it would require a large number of lawn mowing machines and a relatively large labor force to keep the grass adequately mowed. This would make the cutting of these grassy areas extremely expensive.
Various self-propelled "large scale" mowing machines have been designed to more efficiently cut large areas of land covered by grass. One general type of such a mowing machine is that known in the industry as a tri-plex machine. The tri-plex machine is a self-propelled mowing machine of the rider type (i.e., one which carries an operator) having an internal combustion engine as the basic power source. The machine comprises a frame or body member which is movably supported by a plurality of drive wheels. Three drive wheels arranged in a triangular relationship are sometimes used. In addition, the body of the tri-plex mowing machine usually supports three cutting units which are vertically movable into and out of engagement with the ground. Each of the cutting units comprises a rotatable reel type blade which sweeps the grass against a fixed bed knife to cut the grass. The drive for the cutting units and the drive wheels is usually taken off the internal combustion engine by generally conventional power transmission systems (e.g., mechanical belt drives and the like).
One feature of many tri-plex mowing machines is the use of mechanically operated brake systems for braking the drive wheels of the machine. In such brake systems, an actuating lever is connected to each of the brakes of opposed drive wheels. Each of these levers are connected in turn to opposed brake rods carried on either end of a brake shaft. When the brake shaft is rotated by the operator through manual actuation of a brake pedal, the brake rods pull on each of the actuating levers to actuate the drive wheel brakes in an amount which is proportional to the force applied to the actuating levers. When the force applied to each of the levers is not equal, unequal braking occurs on the opposed drive wheels of the machine. This causes the mowing machine to veer to one side or the other which disrupts the grass mowing pattern.
It has previously been necessary for the operator to adjust the brake rods relative to the actuating levers (e.g., by threading the brake rod into or out of a yoke which connects the brake rod to the actuating lever) to achieve equal braking action on each of the opposed drive wheels. The adjustment process is often one of trial and error. In other words, a large number of adjustment operations may be required to find the proper position of the brake rods which cause the drive wheel brakes to lock equally upon depression of the brake pedal. In addition, operation of the mowing machine over rough or uneven terrain may jostle the brake rods out of their proper positions. This requires that the machine be stopped and the brake rods be readjusted. The need for such continual adjustment of the brake rods, especially by a trial and error method, is both time-consuming and frustrating to the machine operator.
Tri-plex mowing machines also often utilize separate support rods or shafts for many of the controls which are actuated by the operator. More particularly, these machines often include a gas or traction pedal which regulates the ground speed of the machine and a steering assembly which transfers a steering force from a manually actuable steering wheel to one or more of the drive wheels. The traction pedal, the steering assembly and other similar controls have customarily been individually mounted on separate support rods or shafts. These shafts are separate from the brake shaft. Use of such separate shafts increases the manufacturing costs of the machine since a plurality ofshafts are required along with corresponding support structures which rotatably mount the shafts in the machine, such as bushings, etc. In addition, the body of the mowing machine must usually be enlarged to accomodate these shafts since the shafts must be appropriately spaced from one another to allow free rotation thereof.